The invention relates to a method for making a hole in the ground, according to which one brings at least two lines in the ground which connect with one end thereof to one and the same head, lines from which one communicates with at least one spray opening which opens on that end lying forward in the direction of the hole to be made, of the head, outside said head, and the other one communicates with at least one sidewise-lying opening in the head, whereby the head is driven into the ground notably by pumping fluid under a first high pressure through that line which opens on the opening in the forward-lying head end, and pumping at least temporarily fluid under another second pressure through the other line.
The head itself may be provided with a cutting tool and possibly with a fluid-operated motor to drive said cutting tool.
Such a method is known from FR-A-2,493,907.
According to said known method, one discharges through a first line, the nature of which is not further described and which communicates with spray nozzles on the head front end, fluid under a very high pressure from 500 to 4000 bars to make the hole in the ground. Through a second line lying adjacent thereto, the nature of which is not further described either, fluid under a lower pressure is pumped through a turbine mounted in the head and through openings in the head side, along the outer head side towards the frontmost end. Said fluid is used on the one hand to drive the turbine, and on the other hand to flush the hole clean and thus to remove the waste. The turbine is used to impart a rotating movement to the rotatable head end.
The head is directed in the ground by means of a guide which is mounted on the head and which comprises three units which are arranged about the head. By means of hydraulic jacks, which are operated with fluid which is fed through a third line, the guide is displaced stepwise in the hole together with the head, while by means of other hydraulic jacks, some direction can be given to the guide relative to the already-bored hole and thus some direction can be given to the head and consequently to the direction of the hole still to be drilled.
Due to the requirement of having to use a guide and to feed fluid through three lines, said method is relatively costly. As the guide has to be moved stepwise, the method is not simple. Further the directing is very difficult to perform accurately. The hydraulic jacks for the directing bear during such directing on the wall of the already-formed hole. Such jacks can thereby enter into the hole wall when such wall is not very strong, which makes accurate directing impossible.
The invention has for object to obviate such drawbacks and to provide a method for making a hole in the ground which is inexpensive, simple and fast and still makes possible directing accurately the head and consequently determining accurately the hole direction.